On the potential curve of the metastable helium molecule

The potential curve for the 2sσ 3Σu + of the helium molecule is computed using the valence bond method with configuration interaction. The wavefunction used is a seven-term mixed basis set of Slater and elliptic type orbitals and is constructed according to the criteria of Gupta and Matsen. The curve shows a potential maximum at 4·66 a 0 and has a barrier of 0·14 eV. The vibrational and rotational constants are compared with earlier calculations as well as the experimental values and are found to be in fairly good agreement with the latter.